Getting started with Jest automation testing

Thorough testing is necessary for developing and releasing a high-quality, well-functioning application. Test automation is a crucial component of application development because it creates an automated procedure allowing one or more test types to run without manual intervention. Additionally, it expedites the entire development process and guarantees that the newly created code performs exactly as expected without causing any regressions.

Jest is one of the most well-liked and simple-to-use testing frameworks for developers working on a JavaScript/Typescript codebase for test automation. It is a very effective tool to build using TDD due to its simplicity. It works well with many well-known IDEs for JavaScript.

We will discuss Jest automation testing in this article, including a brief introduction to Jest, a list of its capabilities, and limitations, the primary factors that make Jest a well-liked testing tool, instructions for installing Jest, and more.

What is Jest?

Testing front-end and back-end apps are made possible via the open-source Jest testing framework, which is based on JavaScript. Its objective was to examine JavaScript-based software. Recently, Jest has become quite popular because of its emphasis on simplicity.  Jest was created by Facebook, and having all the components required in a single framework speeds up and simplifies the process of running JavaScript tests.

This framework is comprehensive because a large portion of its functionality is provided by internal resources rather than external tools. Jest is a comprehensive testing framework that has raised modern testing to a new level. It offers a blended package comprising an integrated assertion library, a built-in mocking library, and a test runner.

It is excellent for validation because it has tools that are well-managed, adequately documented, and organized in a way that makes developing tests easier. Due to the mocking and assertion libraries that are already integrated into it, tests may be executed more quickly and without fuss when they are run simultaneously. To speed up and simplify things, it runs previously failed tests first before rearranging the runs of the next tests, which are based on the lengthy test files.

It is a well-defined document that needs little setting and can be expanded as needed to meet the needs. Jest makes testing enjoyable. It was first created for testing React and React Native-based web applications, but it currently functions flawlessly with every modern JavaScript framework, including React, Angular, Vue, and Node.

It is quite simple to use and can be set up with npm or yarn. This enables developers to quickly write tests with Jest. Additionally, the jest framework aids developers in validating the precision and accuracy of all JavaScript-based code, regardless of whether it is used to create mobile applications or browser-based web applications.

This framework is primarily used for React testing by many large organizations, including Facebook, Twitter, Instagram, Pinterest, Spotify, and Airbnb.

After a brief introduction, let’s talk about some of Jest’s features.

Features of the Jest Framework

Some of the features of Jest are-

Quick and effective – Jest’s framework is quick and safe. It rapidly executes all of the test cases without any lag time. Jest runs failed tests first and reorders test runs according to how long test files take, which makes it perform quickly and efficiently. Additionally, as tests are conducted concurrently, multiple configurations are tested at once.

Code coverage – Jest has excellent code coverage, which is the percentage of the code that is currently covered by unit tests. By utilizing the coverage command, Jest can generate code coverage. The coverage report can be produced with no further setup. This can be used to verify the test cases and forecast the number of additional test cases required to get greater coverage.

Strong Mocking support- Mocking is a strategy for separating different test subjects. This separation is accomplished by swapping out dependencies for objects that may inspect and manipulate the test subjects. Jest replaces dependencies with mock functions, which makes building mock functions quite simple.

Since the tests use a custom resolver for imports, it is simple to mock any object that is not within the scope of the test. Jest supports all varieties of mocking, including functional mocking, timer mocking, and simulating specific API calls.

Simple to set up and requires no configuration- Jest, greatly simplifies the process and requires no configuration. The majorities of modern JavaScript frameworks include it out of the box and don’t require any configuration. With only a few minor tweaks or configurations, Jest may be deployed as a dependency and used to start creating tests and deploying them.

Isolated working of all tests- Jest tests are executed in parallel to reduce runtime. The fundamental principle of isolation is to set up each test’s environment so that it will only consider executing one test at a time. This prevents any one test from interfering with another test’s operation or affecting the results of other tests. This characteristic makes the jest framework operate more quickly.

Support snapshot testing- Snapshot testing can be made possible by Jest. It enables checking the accuracy of huge objects. As a result, it is not necessary to create lengthy tests filled with assertions to determine whether each attribute is available and is of the appropriate type on an object. Jest will handle everything if you only create a snapshot.

Thorough API- Jest is well-known for having a comprehensive API that offers numerous specialized assertion types for particular needs. In addition, its great documentation makes it easy to start using it immediately.

Jest supports TypeScript – Since Typescript is used to create JavaScript applications that can be executed on the server or the client, it may be implemented using the ts-jest package. The best aspect of Typescript, which is a well-known superset of javascript, is that it uses plain javascript. Along with providing a source map for Jest and acting as a typescript preprocessor, the ts-jest package has a very responsive community.

Now that you are familiar with Jest’s characteristics, let’s examine its intended use.

Why use Jest

Listed below are a few reasons for selecting Jest for test automation:

  • Quick and easy, perfect for prototyping.
  • Comes with an interactive mode that launches all affected tests automatically for the code changes made in the most recent commit.
  • Provides a CLI tool to make it simple to control the tests;
  • Provides .only and .skip syntax to test a single test or a set of tests. When troubleshooting particular tests, this function is useful.
  • Enables the creation of code coverage reports by simply adding the parameter, coverage to the command line.
  • Rich and valuable error reporting is provided during test execution.
  • Offers great documentation, lots of examples, and a helpful community.

Limitations of the Jest Framework

  • Among JavaScript developers, Jest is a newer and less popular framework. The Jest testing library may be difficult to understand for those who have used other testing libraries.
  • A popular IDE like WebStorm does not support Jest.
  • Jest offers fewer tools and library support than other comparable libraries.
  • Jest snapshot testing is not appropriate for tasks that produce big, thousands-line snapshot files.
  • Jest runs slower because of the auto-mocking feature.

When to use Jest

Jest can be used to test complicated data structures, while it is most frequently used for simple API (Application Programmable Interface) testing scenarios and assertions. Unit tests and additional Javascript libraries are both supported. Additionally, it works well for user interface testing.

Installation of Jest

Although installing Jest is not a particularly difficult procedure, there are a few requirements to meet beforehand. Here are some essential Jest libraries and packages that must be installed on the system to run Jest test scripts. So let’s examine them.

NodeJS and Node Package Manager (npm)- NodeJS can be installed either from the org website using the Windows Installer binary or using the npm manager. An open-source software library called Node Package Manager, or a command-line tool, is typically used to update, install, or remove different Node.js packages in web-based or mobile apps. It has about 8 lakhs code packages. Navigate the npm-command line tool and install the most recent version to start the npm command.

Selenium WebDriver- Selenium WebDriver is a web framework that enables the execution of cross-browser tests. It enables developers to create numerous test scripts in any programming language that fits them. Selenium WebDriver is used to automate the testing of any web-based or mobile application to see if it functions as intended or not.

When testing on a local Selenium Grid, Jest requires the Selenium WebDriver to be installed on the machine. The jest module is dependent on the Selenium web driver. The root directory contains the Jest module installation. The most recent version of Selenium WebDriver can be installed after setting up npm on the system.

Java SDK- The Java -SDK jest keyword can be used to execute commands from the command line. Make sure that the system has finished installing the Java Development Kit and has been configured with the Java environment before continuing with the installation of the JEST framework. This is because Jest is a Selenium test framework and Java is one of the most widely used languages for creating Selenium automation testing scripts.

The ‘-g’ flag, which may also be used with the npm command, can be used to install the jest module on a global scale. The’- g’ flag makes it simple to use the various Jest commands without first creating the package file for npm tests.

Execute Jest tests on LambdaTest.

Jest is a Selenium test framework, and Java is the foundation of Selenium. LambdaTest is a cloud-based cross-browser testing platform that offers a Jest cloud grid and a cloud Selenium grid comprising more than 3000 real devices, browsers, and operating systems online for performing Jest and Selenium testing at scale.

With the help of LambdaTest’s advanced reporting platform and Jest’s JavaScript-friendly test framework for React and React Native apps, testers can quickly build test automation for their web applications that will run concurrently across various platforms and browsers. Through comprehensive test reporting, in-depth test artifacts, and test logs, testers can develop and run their JavaScript test suites at scale in a secure cloud-based environment and receive immediate feedback. This gives them insights into how their apps function.

The DevOps pipeline can also be effortlessly linked with LambdaTest. As a result, any CI/CD system may be used to create and run Jest test scenarios.

So use LambdaTest’s in-depth Jest tutorials to gain a deeper functional understanding of the framework and begin your Jest automation journey by executing your first Jest test script on the LambdaTest cloud.


In conclusion, Jest is one of the most widely used testing frameworks for online testing and is easy to use, reliable, and versatile. It comes with a wide range of test productivity tools, including minimal configuration, code coverage, comprehensive APIs, mocking capabilities, and more.

It promises to offer a scalable testing solution for web applications created with TypeScript, Node, React, React Native, Angular, Vue, Babel, and other programming languages across web and mobile platforms. Jest can be utilized at both the front end and the back end if you are using JavaScript as your programming language.